RUNALYZE Understanding the calculations

Understanding RUNALYZE calculations right away is not always easy. Especially when you haven’t dealt with the topic of analyses & calculations while running at all.

The Effective VO2max

VO2max is a scientific metric for the maximal oxygen uptake that is highly correlated with one’s maximal running performance. Still, two athletes with equal VO2max values do not need to perform equally as their efficiency may differ. Instead of the exact VO2max (which can be measured in a lab), the combination of VO2max and running efficiency is of intereset. The resulting Effective VO2max can be used as direct predictor for upcoming running events.

Runalyze estimates the Effective VO2max for every run with heart rate data based on the relation of heart rate and pace. Optionally, elevation can be taken into account as well. The average of these values will be used as the athlete’s current shape. As everybody’s heart rate may behave differently, Runalyze uses an additional individual correction factor which is calculated based on one’s best race and its heart rate automatically. Alternatively, athletes can pick a manual correction factor.

To be able to estimate the effective VO2Max and the resulting forecasts as well as possible, it is important that you declare competitions as such.

Important: Every runner is different – the predictions do not always fit right away. Which settings you have to adjust the forecasts you can read in this help article.

Marathon shape

The marathon shape is an invention of Runalyze to optimize prognoses for long distances, that are based on the effective VO2max. These prognoses normally can’t consider whether the athlete has the optimal fitness or endurance for a marathon. The marathon shape is the solution for this problem, as the prognoses are continually adjusted for missing fitness.

To calculate the marathon shape, the kilometers made a week aswell as every single run according to length are looked at. Other physical activities (e.g. cycling) are not going to be considered. The target is set to a calculated value according to the athlete’s current best possible marathon time, based on the VO2max. The kilometers and the distance of the weekly long run are derived from typical marathon training plans.

By default, these calculations are based on the training of the last six months, while the kilometres made a week count 2/3 and the long distance runs account for 1/3 of the ‘Marathon shape’. These parameters can be changed individually by every athlete.

What percentage of the marathon form would be enough for a half marathon?

For a 10 km run 17% GA is enough, for a half marathon 42.5% and for the marathon 100%. For a 100 km run, for example, it is 288%.


Acute Training Load represents your current degree of fatigue, being an exponentially weighted average of your training load (i.e. TRIMP) over a period of 7 days by default.

Absolute values of ATL are hard to interpret, as preferred values vary from athlete to athlete depending on their current level. Instead of showing absolute values, Runalyze uses the alltime maximum ATL to express current ATL as percentage. In this way, ATL values are always relative to the athlete’s maximum. Still, if an athlete was overtraining once, reaching 100% ATL is not recommended.

Fitness level

Chronic Training Load represents your current degree of fitness, being an exponentially weighted average of your training load (i.e. TRIMP) over a period of 42 days by default.

Similar to ATL, Runalyze uses the alltime maximum CTL to express current CTL as percentage.

Stress Balance

Training stress balance is the difference between CTL and ATL (in absolute values) and can help as indicator for hard training (negative values) and rest (positive values). If an important race is ahead, TSB should be clearly positive. As levels of CTL and ATL differ from athlete to athlete, no concrete suggestions can be made.


Easy TRIMP is the maximal allowed TRIMP for the following day that will keep TSB at 0, i.e. keeps a balanced training stress.

If you have exceeded this value, the “Easy TRIMPs” recommendation is replaced by a number of rest days.


The training monotony is a method for evaluating the similarity of the daily training and is based on the variation of the daily TRIMP values over the last seven days. The lower the variation the higher the monotony. Results underneath 1.5 are considered as recommendable, results above 2.0 as critical. To recognise overtraining, one should bear training strain in mind as that value rates monotony and training load together.

Notice: This calculation is based on the sum of the *all day* TRIMP value. It is based on the overall strain made a day, no matter which kind of activity has been done.

Training strain

The training strain calculates the risk of overtraining by combining training monotony and the sum of all TRIMP values for a given period. The risk of overtraining has an individual limit for every single athlete.

Runalyze tries to estimate the athlete’s limit by current ATL and gives a coloured (green/orange/red) feedback.


Prognoses for ultraluns

Predictions for such long distances are extremely difficult to make and are hardly covered by the usual formulas.

The formulas we use are very optimistic for ultramarathons. But we can’t change that – the formulas are simple. We try to counteract this with our “basic endurance”. In other words: Only those who run the necessary kilometres will be able to reach the marathon prognosis.
The necessary basic endurance is calculated as `distance ^ 1.23`. That means: 17% GA is enough for a 10 km run, 42.5% for a half marathon and 100% for the marathon. For a 100 km run, for example, it is 288%.

Assuming one only has 144 % of this ominous “basic endurance”, the VO2max would be multiplied by 0.5.

How the basic endurance is calculated can be displayed in the extra window “How are these values calculated” (magic wand as icon). The specifications for the long run and the weekly kilometres are based on the current VO2max and are derived as a rule of thumb from typical marathon training plans.

The influence of basic endurance could be reduced slightly by increasing the factor of weekly kilometres in the configuration under “Basic endurance” (must be between 0.00 and 1.00, e.g. 0.80).

Other models are the best remedies. But they all depend on past competitions and not on the current training. Robert Bock’s model is most suitable for ultra-races because it calculates a “fatigue factor” from two actual results.

Any more questions? We collect some questions from the forum/on Facebook and try to answer them here in general

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We spend our leisure time to make RUNALYZE as good as possible and we still have tons of great ideas, but time is scarce and after a hard training we first need some fruits or a smoothie. You can support the development of RUNALYZE with every financial contribution — We highly appreciate every grant.

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